The ends of human chromosomes are protected by DNA-protein complexes called telomeres. In adult somatic cells, telomeres progressively shorten until reaching a critically short length, resulting in senescence or crisis. This process limits the proliferative capacity of most cell types. Telomerase is the enzyme responsible for synthesizing the repetitive DNA that comprises the telomere. Our lab is primarily focusing on understanding the molecular basis for the intracellular trafficking of the core components of telomerase: telomerase RNA (hTR), and telomerase reverse transcriptase (hTERT). We hypothesize that the recruitment of telomerase is triggered during S-phase of the cell cycle and is facilitated by the dynamic association of the enzyme with core telomere binding proteins. Fluorescence microscopy techniques developed by our lab will be employed in a variety of assays to assess the intrinsic roles of telomerase, as well as those of a panel of core telomere binding proteins, in facilitating recruitment to telomeres. We have defined two specific aims: Aim1-The role of hTERT in targeting telomerase to the telomere end will be dissected. This will be accomplished by testing the ability of a panel of hTERT mutants to target telomerase to telomeres in multiple cell types. Additionally, in vitro binding assays will determine which domains of hTERT are critical for binding TPP1, the central recruitment candidate among core telomere binding proteins. Aim 2-The role of core telomere binding proteins in mediating telomerase recruitment to telomeres will be determined. The effects of RNAI mediated depletion and retroviral vector assisted overexpression of each core telomere binding protein on the recruitment of both hTR and hTERT will be contrasted. Recruitment candidates identified in this manner will become the focus of additional mutational analysis to identify their contribution(s) to telomerase recruitment. Public Health Relevance: Cancer has become a serious threat to the health of our society. This disease does not discriminate, proving to be a leading cause of death shared among the diverse racial and ethnic groups that make up the american population. Telomerase is reactivation is critical to prolonged tumor maintenance and proliferation in nearly all cancers. The characterization of hTERT association with core telomere binding proteins should contribute significantly to our understanding of the dynamic mechanism of telomerase regulation through recruitment and trafficking. This may prove invaluable in developing new ways to inhibit telomerase and combat the vast majority of cancers.